Electrode for sparking plugs and their manufacture



June-16, 1953 QG. bowsoN 2,642,053

ELECTRODE FOR SPARKING PLUGS AND THEIR MANUFACTURE Filed July 13, 1949 A A F16. 7

INVENTOR ARTHU GORDON. DOWSDN BY Q/ZZ MW ATTORNEY Patented June 16, 1953 ELECTRODE FOR SPARKING PLUGS AND THEIR MANUFACTURE I Arthur Gordon Dowson, London, England, as-

signor to Baker & Company Incorporated, Newark, N. J a corporation of New Jersey Application July 13, 1949, Serial No. 104,484 I In Great Britain July 16, 1948 1 Claim. (01. 123-169) amount of platinum alloy required, it has been proposed to attach to a'base metal electrode, for example by electrical resistance welding, a tip of a more resistant metal such as an alloy of platinum, covering only that part of the electrode which is exposed to the action of the spark.

In the case of the earth electrodes, only that side which is adjacent to the centre electrode is exposed to the eroding effects of the spark; and,

therefore, in order to economise the use of the relatively very expensive tipping metal, it would be most useful if the tip could be confined to that side. The attaching of such tips to wire of the small dimensions involved is, however, a very difficult operation, and it is the main object of the present invention to devise a method of manufacture which will simplify the production of earth electrodes tipped in the manner described, and render their production commercially feasible.

In accordance with the invention, there is provided a method of making tipped electrodes wherein a strip of base metal has a longitudinal strip of nobler tipping metal attached thereto, the composite thus produced being cut transversely across its length to obtain individual tipped electrodes.

For a better understanding of the nature of the invention, two examples of procedure will now be described in detail, with reference to the accompanying drawings, in which:

Figure 1 is a plan view of a strip formed at an initial stage of manufacture of the electrodes;

Figure 2 is an end view corresponding to Figure 1;

Figure 3 shows a formed electrode in plan;

Figure 4 is a plan view of a second type of strip formed at an initial stage of manufacture of the electrodes; 7 Figure 5 isan end view corresponding to Figure 4; i

electrode of the invention. 7

Figure 6 shows two formed electrodes in plan;

Referring first to Figures 1, 2 and a of the drawings, there is indicated a strip of base metal l the width of which is equal to the length of the finished electrode 2. Along one side edge of the strip there is inlaid a thinner strip 3 of precious metal, the latter being attached to the base metal.

by welding or soldering. Both the base and precious metal strips are of thickness greater than is required for the finished electrode, and after the inlaying operation has been completed, the composite thus produced is rolled to the required thickness of the electrodes to be formed. The strip is then cut at right angles to its length into reactangular or square pieces. A line of cutting is indicated at A-A in Figure 1. Each of these pieces will in effect be a wire having a short length tipped as at 4 with the precious metal. It will be noted that the thickness of the precious metal tip 4 can be made as little as desired by adjusting appropriately the ratio of thickness of the inlay 3 to that of the base metal I when in strip composite form, and by carrying the rolling operation to the desired extent. Moreover, by joining the precious metal inlay strip 3 to the base metal strip I when both strips are in relatively massive form, it is in practice easier to ensure that the junction is without faults. It is important to observe in this connection that subsequent rolling of the composite will be possible only if the junction is of very high quality, so that the finished electrodes will necessarily have tightly affixed tips. In this way the likelihood of failure in the employment of the finished electrodes is much reduced, because the tip will not readily part from the base metal portion of the electrode.

The method set forth above can be slightly modified with advantage, and reference will now be made to Figures 4, 5 and 6. Thus the base metal strip 5 could be made of width equal to twice the length of the desired finished electrode 6. The inlaid strip of precious metal 1 is then made centrally down one face of the base metal strip 5, the width of such inlay being twice the length of the desired precious metal tip 8 upon the finished electrodes. After the rolling operation of the composite strip, the latter can be longitudinally cut down its centre to give two composite strips which can thereafter be transversely cut to produce the electrodes. The lines of cutting are indicated at XX and Y--Y. It is advantageous to proceed in the manner just indicated since during the rolling operation undesired lateral spread of the precious metal inlaid strip will be reduced to a minimum.

The composite strip would be applied to a spark plug as shown in Figure 7. The spark plug l0 3 has a center electrode 12 embedded in a ceramic insulator M. The earth electrode 2 is afiixed to the metal shell I8 of the spark plug, and is formed with the precious metal inlay tip at 4 as previously indicated.

From the description given above, it will be realised that the necessity for handling and attaching very small precious metal tips to finished size Wire is eliminated. Thus the relatively difficult operation of preparing the face of the base metal wire to receive a tip, is avoided."

It will be realised that the invention isnoti confined as to the nature of the base and precious metals, except insofar as both'metals -must be capable of being rolled to strip.' It will also be obvious that an electrode can be made with a strip of precious metal on either side thereof by '1 Number,

4 therebetween, at least saidearth electrode being formed of a strip of base metal and having a longitudinally extending recess in one end thereof, said recess being juxtaposed to the center electrode on that side of the earth electrode which is exposed. to the eroding effects of the spark, said recess extending transversely the full width of said strip, a precious metal inlay tip bonded to said strip within said recess, whereby 10 the area of the electrode exposed to the eroding efiects is made resistant thereto.

' ARTHUR GORDON DOWSON.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Clement July 28, 1914 Eldred Mar. 2, 1915 Reeve Nov. 4, 1941 Heller Sept. 15, 1942 Hensel Dec. 25, 1945 

